Interdigitated heterostructure finger optoelectronic mixers

Summary form only given. Optoelectronic mixers have been implemented in many microwave and communication applications. Recently, B. Stann and others successfully demonstrated FM/CW laser ranging using a metal-semiconductor-metal (MSM) detector as a mixer. In this application, a local oscillator (LO) voltage modulated at multi-GHz is applied to the detector causing mixing with the modulated received light. For such an application, the detector/mixer must have high detecting/mixing efficiency, high bandwidths, and low LO drive loads. In addition, the detector/mixer should have no average response to unmodulated background light. We present a new optoelectronic mixer, which is essentially an planar interdigitated finger version of an n-i-n structure. We used n-AlGaAs in the form of interdigitated fingers. These fingers are transparent at the wavelength of interest (850 nm), which greatly increases the responsivity. The band offset at the AlGaAs/GaAs interface is used to provide a controllable barrier to reduce the dark current. The interdigitated configuration provides a low capacitance and a balanced response under background illumination. The samples used were grown by molecular beam expitaxy. Standard lithography was used to form the AlGaAs interdigitated fingers.